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Biomedical subjects

J Rojas

Publications and source records attributed to J Rojas.

At least 91 records · Page 5Linked to original sources
PubMed1981

Studies on group B beta-hemolytic Streptococcus. I. Isolation and partial characterization of an extracellular toxin.

To initiate an investigation into the biochemistry and mechanism of group B beta-hemolytic Streptococcus virulence, bacterial cultures grown in suspension were centrifuged, and the bacteria and media were subjected to extensive fractionation. Each fraction was assayed for physiologic activity by repeated intravenous infusion into adult unanesthetized sheep. Pulmonary artery pressure, arterial PO2, and rectal temperature were monitored. The media fraction, but not the bacteria, contained a component (molecular weight, 2 x 10(6)) composed of 845 carbohydrate and 16% protein with physiological activity. Two mg quantities, when infused, caused the pulmonary artery pressure to increase 100%, PO2 to decrease by 20% and chills and fever. The active component could be degraded by hot phenol-water extraction into a pure polysaccharide (molecular weight, 200,000). This lower molecular weight polysaccharide retained the identical physiologic properties when infused in the sheep. The degraded component precipitated with group B-specific antiserum. This study demonstrates that, in the sheep, a pure polysaccharide is the physiologically active part of a high-molecular-weight toxin synthesized by group B beta-hemolytic Streptococcus type III and that this component has a different carbohydrate composition from the group B capsular antigen.

Animals↗
PubMed1981

Studies on group B beta-hemolytic Streptococcus. II. Effects on pulmonary hemodynamics and vascular permeability in unanesthetized sheep.

To study the effects of Group B beta-hemolytic Streptococcus on the pulmonary circulation and lung fluid balance, live and heat-killed bacteria and their toxin were infused into an awake sheep lung-lymph preparation. In every case, the response was biphasic; there was an initial period of marked pulmonary hypertension and high flow of protein-poor lymph associated with tachypnea, chills, and fever. A second phase followed during which pulmonary vascular pressures returned to near baseline and remained stable, but lymph flow remained high. The changes seen in the initial phase resemble the previously reported response to mechanically increased pulmonary vascular pressure and suggest that the increase in fluid filtration is secondary to increased microvascular pressure. During the second phase after toxin infusion, the increase in lung lymph flow was paralleled by an increase in lymph protein clearance. This cannot be accounted for by the hemodynamic changes alone an suggests that the permeability of lung microvascular walls to protein was increased. It is concluded that group B beta-hemolytic streptococcal toxin in the sheep model causes pulmonary hypertension and increased pulmonary vascular permeability.

Animals↗
PubMed1980

Lung water and vascular permeability-surface area in newborn lambs delivered by Caesarean section compared with the 3-5 days-old lamb and adult sheep.

Extravascular lung water and vascular permeability-surface area products were measured with a multiple indicator dilution method in five unanaesthetized newborn lambs 2 to 7 h following delivery by Caesarean section at a gestational age of 135-142 days. The indicators used were 51Cr-labelled erythrocytes, [125I] albumin, [3H] water and [14C] urea. Post-mortem determination of extravascular lung water and dry bloodless lung weight were also performed. The results were compared with previously obtained data in unanaesthetized 3-5 days-old lambs and adult sheep. Normalized to dry lung weight, extravascular lung water by both techniques was significantly higher in lambs after Caesarean section than in either the 3-5 days-old lambs or the adult sheep (P less than 0.05). (Indicator values = 3.9 +/- 0.2 (SEM) ml/g for Caesarean section lambs, 3.1 +/- 0.3 for 3-5 days-old lambs and 3.3 +/- 0.5 for adult sheep; post-mortem values were 6.12 +/- 0.28 g/g for after Caesarean section lambs, 4.07 +/- 0.26 for 3-5 days old lambs and 4.03 +/- 0.17 for sheep). Vascular permeability-surface area product for [14C] urea, computed by a mathematical model, was significantly higher (P less than 0.05) in lambs after Caesarean section than in adult sheep (0.18 +/- 0.02 compared with 0.10 +/- 0.03). In 3-5 days-old lambs the value was 0.16 +/- 0.04. It is concluded that, when normalized to dry lung weight, lung following Caesarean section delivery near the end of gestation. Adult values for lung water have been reached by the age of 3-5 days.

Adaptation, Physiological↗
PubMed1979

Pulmonary vascular response to prostacyclin in fetal lambs.

Eighteen prostacyclin injections (19.4 +/- 1.5 micrograms/kg) were performed in five chronically instrumented, intact fetal lambs in order to study the effects on pulmonary blood flow. These resulted in a brief period of bradycardia followed by a more prolonged period of increased pulmonary blood flow. In this latter phase, pulmonary blood flow increased from a baseline value of 49 +/- 4 ml/(kg min) to 122 +/- 10 ml/(kg min). Systolic/diastolic pulmonary arterial pressure simultaneously fell from 73 +/- 2/48 +/- 1 to 68 +/- 2/42 +/- 1 mm Hg. Flow through the ductus arteriosus was unchanged and right ventricular output increased to account for the increased pulmonary blood flow. Thus, prostacyclin causes pulmonary vasodilation in intact fetal lambs and may participate in the control of fetal pulmonary blood flow and the circulatory adjustments to extra-uterine life.

Animals↗
PubMedDate not supplied

Number and size of stones in patients with asymptomatic and symptomatic gallstones and gallbladder carcinoma: a prospective study of 592 cases.

The development of gallbladder carcinoma has been correlated with the presence of a single large gallstone in two retrospective studies. The objective of the present study was to determine the number and size of gallstones in patients with gallbladder carcinoma compared to asymptomatic and symptomatic female patients with gallstones. The following three groups of patients were included in this prospective trial: (A) 78 asymptomatic patients with gallstones; (B) 365 symptomatic patients with gallstones; and (C) 149 patients with gallbladder carcinoma. At the end of the operation, the resected gallbladder was opened and the number of stones counted. The maximum size of the stones was determined using calipers. Patients with gallbladder carcinoma were significantly older than patients in the other two groups (P <0.001). In the group with asymptomatic gallstones, there were significantly more patients with one single stone, whereas in the group with gallbladder carcinoma there were significantly more patients with multiple stones (more than 11; P <0.01). Patients with gallbladder carcinoma had significantly larger stones, regardless of the number of stones present (P <0.001). We postulate that the increase in the number and size of the stones among patients with gallbladder carcinoma could simply be an effect of aging or it could be a reflection of the long-term presence of stones in the gallbladder rather than some particular chemical or physical influence.

Adult↗
PubMedDate not supplied

Sandfly Lutzomyia longipalpis in a Cutaneous leishmaniasis focus in central Colombia.

Lutzomyia longipalpis, 15 other species of the genus Lutzomyia, and one species of Brumptomyia were collected in an endemic focus of cutaneous leishmaniasis in a river canyon 450 m above sea-level, in Rio Claro, Antioquia, Colombia. The presence of Lu. longipalpis is associated with the destruction of the primary forest and the development of new farmland and rural settlement in this region. The composition of species identified a different habitat for Lu. longipalpis in Colombia. Lu. yuilli and Lu. longipalpis were predominant (68.26%) followed by Lu. trapidoi, Lu. hartmani, Lu. triramula, Lu. panamensis, Lu. gomezi.

Animals↗
PubMedDate not supplied

Ampicillin-loaded liposomes and nanoparticles: comparison of drug loading, drug release and in vitro antimicrobial activity.

In this paper, we report the physico-chemical properties of negatively charged liposomes and of polyisohexylcyanoacrylate nanoparticles loaded with ampicillin. Although the carriers were of the same size (200 nm), drug-loading capacity was 20 times higher for nanoparticles than for liposomes. After freeze-drying or storage at +4 degrees C, no drug escaped from polymeric nanoparticles. On the other hand, in the same conditions, ampicillin leaked rapidly from liposomes. Drug release in foetal calf serum was gradual (of zero order) with nanoparticles, whereas it was rapid with liposomes. Finally, the antimicrobial activity of ampicillin-entrapped liposomes or nanoparticles was studied in vitro.

Ampicillin↗
PubMedDate not supplied

Changing the pH of the external aqueous phase may modulate protein entrapment and delivery from poly(lactide-co-glycolide) microspheres prepared by a w/o/w solvent evaporation method.

The milk model protein, beta lactoglobulin (BLG), was encapsulated into microspheres prepared by a multiple emulsion/solvent evaporation method. The effect of the pH of the outer aqueous phase on protein encapsulation and release as well as on microsphere morphology has been investigated. At all tested pH values, the encapsulation efficiency was shown to decrease with increasing the initial amount of BLG. This was correlated with the reduced stability of the primary emulsion as the initial BLG increased. In addition, reducing the solubility of BLG in the external aqueous phase by decreasing the pH to the isoelectric point of BLG (pI 5.2) resulted in an improved protein encapsulation. Moreover, it was shown that combining pH modification and optimal stability of the first emulsion yielded microspheres with a high encapsulation efficiency. However, release kinetic studies revealed that a significant burst release was observed with microspheres loaded with large amounts of BLG, especially when prepared in a medium at pH 5.2. This burst effect was attributed to morphology changes in the microsphere surface which was characterized by the presence of pores or channels able to accelerate the release of BLG. These pores were assumed to result from the presence of large amounts of protein molecules on the microsphere surface, that aggregate during microsphere formation at pH 5.2. Indeed, single adsorption experiments have shown that BLG had a higher affinity for the particle surface when the pH was close to the pI. Thus, reducing the solubility of a protein in the external aqueous phase allows the product of microspheres with a better encapsulation efficiency, although this benefit is provided by a strong adsorption of the protein on microsphere surface.

Adsorption↗
PubMedDate not supplied

Gallbladder carcinoma during laparoscopic cholecystectomy: is it associated with bad prognosis?

Laparoscopic cholecystectomy is the treatment of choice for gallstone disease. The ultrasonogram has failed for the early detection of gallbladder cancer, especially if inflammation (chronic or acute) is present. Incidental gallbladder could be an important cancer finding during laparoscopic cholecystectomy, due to the potential cancer cell dissemination during the procedure. In our Department, 6500 laparoscopic cholecystectomies have been performed in the last 5 years and in 15 cases (0.23%) gallbladder cancer was found during surgery or after histological examination of the resected gallbladder. In none of these 15 patients was pre-operative diagnosis of gallbladder carcinoma postulated. When re-evaluation of the pre-operative ultrasonograms was done, it was possible to observe signs suggesting the presence of neoplastic infiltration in 4 of them (28.6%). During videoscopic exploration, also in 4 patients, the suspicion of gallbladder cancer was noted. Laparoscopic cholecystectomy was completed in 9 patients. In 2 of them, in situ or mucosal invasion was demonstrated with a long survival. One patient presented recurrence at the biliary hilum 2,5 years after surgery. Six patients were re-operated and in 4 of them peritoneal or port site metastasis was found; all died early (4.5 month median survival). The other 2 patients were submitted to liver bed resection and lymph node dissection. These patients are free of cancer recurrence after 15 months of follow-up. Six patients were converted to open surgery, performing palliative procedures and died before the 12 month follow-up. The suspicion of pre-operative gallbladder cancer is generally unlikely to be confirmed based on ultrasonographic signs; but, in some cases with high suspicion, further investigation (TAC, tumor markers, etc.) must be indicated in order to avoid poor results. Laparoscopic cholecystectomy could be associated with bad prognosis, and then, when gallbladder cancer is suspected during the laparoscopic procedure, conversion to open surgery could be the best choice.

Carcinoma↗
PubMedDate not supplied

Liver transplantation and hepatitis C virus. Results in a Spanish center since 1989.

BACKGROUND/AIMS: Hepatitis C-related liver disease is the main indication for liver transplantation in many centers. Viral RNA remains after transplantation in almost 100% of the patients, and more recent reports show a graft hepatitis rate of about 90%. The progression of this hepatitis seems to be quicker than in the nontransplant setting. METHODOLOGY: From June 1989 to October 2000, 197 adult patients had 213 for HCV-related liver disease at our institution. Basal immunosuppression consisted of a triple therapy with cyclosporine, azathioprine and steroids, or dual therapy with tacrolimus and steroids. None of the patients was treated with antivirals after liver transplantation. RESULTS: Pure HCV-related cirrhosis was the indication for liver transplantation in 114 patients, another 14 with hepatocellular carcinoma, 8 associated metabolic diseases, 43 high alcohol intake, 4 hepatitis B, 5 cholestatic diseases, and 3 other diseases. Six patients out of the 197 transplanted in this period were already grafted before this time, and had their first retransplantation of the liver after 1989 (their first liver transplantation was done when HCV was not known). Sixteen additional retransplantation procedures were done in the period considered. Hepatitis was diagnosed in 84.3% of the grafts biopsied later than 90 days after liver transplantation (118/140), and in 92.9% if it was done after one year (92/99). Cirrhosis was diagnosed in 21 grafts at a mean time of 1004.7 days, 21.2% of the grafts biopsied after 1 year and 28.6% after 2 years. Nine grafts in 8 patients were diagnosed as fibrosing cholestatic hepatitis. Patient actuarial survival was 80.9%, 69.7%, 67.5% and 50.6% at 1, 3, 5 and 10 years. Liver failure and hepatoma recurrence were the cause of death in 42.4% of the patients. Actuarial graft survival was 75.2%, 64.9%, 63.5% and 48.6% at 1, 3, 5 and 10 years, and was significantly affected by Child stage (B vs. C, P = 0.004). When compared to 228 non-HCV- infected patients with chronic parenchymatous disease, these had an almost significantly better patient survival (P = 0.0577), but a nonsignificant difference in graft survival. Graft loss related to liver causes was 17.6% in HCV+ patients 14.6% in HCV- patients. Liver causes of death were 14.0% in HCV+ patients and 4.8% in HCV-patients (P = 0.002). CONCLUSIONS: HCV infected liver transplantation recipients present very often graft hepatitis, which may progress to advanced stages in a quite short interval. Mid-term patient and graft survival is comparable to those of non-HCV recipients, but causes of death related directly to liver disease are more common in HCV+. This makes one think that long-term prognosis (more than 10 or 15 years) will be worse in HCV patients.

Actuarial Analysis↗